Stimuli-responsive molecular crystals are fascinating for their potential as adaptive smart materials. However, achieving one crystal that could respond to multiple stimuli and perform multiple functionalities simultaneously is still challenging....

It is challenging to expand the abundant photoresponse mode of photoactive functional crystals. In this study, a 2:1 cocrystal of (E)-4-((4-(propyloxy)phenyl)diazenyl)pyridine (APO3C) and tetrafluoroterephthalic acid (TFTA) was designed and synthesized to adjust the robustness of APO3C and to realize new photomechanical motion. The thermal stability of APO3C was enhanced by inserting the coformer. More importantly, photoinduced rotation was achieved under the irradiation of UV light, which was unreported before. A molecular and structural analysis of crystals revealed that the photoinduced rotation can be attributed to three indispensable factors: the linear synthon induced by hydrogen bonding, unsymmetrical isomerization of the APO3C molecules, and their diagonal arrangement. The opposite photoisomerization of APO3C molecules at both ends of a synthon could create torque inside with its diagonal arrangement in three dimensions, producing the unevenness and finally driving the crystal to rotate. The results presented in this work help to enrich the strategy for designing new crystals with novel photoactive functions and expand the diversity of photomechanical molecular crystals through crystal engineering.

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In this work, Fe2O3@TiO2 nanostructures with staggered band alignment were newly designed by an aerobic oil-phase cyclic magnetic adsorption method. XRD and TEM analyses were performed to verify the uniform deposition of Fe2O3 nanoparticles on the nanotube inner walls of TiO2. The steady-state degradation experiments exhibited that 1FeTi possessed the most superior performance, which might be ascribable to the satisfying dark adsorption capacity, efficient photocatalytic activity, ease of magnetic separation, and economic efficiency. These results indicated that the deposition of Fe2O3 into TiO2 nanotubes significantly enhanced the activity of Fe2O3, which was mainly ascribed to the Fe2O3-induced formation of staggered iron oxides@TiO2 band alignment and thus efficient separation of h+ and e−. Furthermore, the PL intensity and lifetime of the decay curve were considered as key criterions for the activity’s evaluation. Finally, the leaching tests and regeneration experiments were also performed, which illustrated the inhibited photodissolution compared with TiO2/Fe3O4 and stable cycling ability, enabling 1FeTi to be a promising magnetic material for photocatalytic water remediation.